Post by thread:Stepper code sample for half step- Strange stepper

Hi everyone I downloaded the following code to a 16c509 jw chip, which controls a stepper based on a couple of buttons, figured out the wires on my stepper (with help from the list), hooked everything up and the stepper displays strange behavior. Sometimes it will turn 1/2 rev then stop and quiver. I accidentally found that if it would only turn if the wire leads coming out of the motor were coiled 180 deg around the motor. When I would hold the shaft and depress the button the motor would turn, unwind the leads then stop a quiver. If I put the leads straight it the motor will just quiver. I checked the connections and 3 other motors that all exhibited this behavior. I am using a ULN 2803 to drive the stepper. ANy ideas? The code I used is designed to half step ther stepper. http://www.beowulf.demon.co.uk. The stepper I am using is unipolar, two phase, 6 lead, 12v, 15 deg per step My question is, are all motors capable of half stepping? What else could be causing this behavior? Can I change the lookup table to get full steps? ; control a small stepper motor with a 12c509 ; There are two controls, run/stop and direction. ; The motor steps when the RUN button is depressed. ; If the DIRECTION button is pressed the direction ; of rotation is reversed. ; ; Peter Lynch, 13 May 1998 ; spam_OUTpicTakeThisOuTbeowulf.demon.co.uk ; (this code is NOT certified Year 2000 compliant) LIST P=12c509 include "\mplab\P12c509.inc" OPMASK EQU B'11000000' BMASK EQU B'00101000' ; all bits output (except GP3 and 5) ; GP3 controls run/stop ; GP5 controls direction RUN_BTN EQU 3 DIR_BTN EQU 5 DELAY1 EQU 0C DELAY2 EQU 0D INDEX EQU 0E ; step index ORG 0 ; start of main code MOVWF OSCCAL MOVLW OPMASK OPTION MOVLW BMASK TRIS GPIO ; now go into a loop, output the next bit pattern on ; GP0 - GP4 (GP3 is input only) CLRF INDEX NEXT ; check for the run/stop button BTFSS GPIO, RUN_BTN GOTO NEXT BTFSS GPIO,DIR_BTN GOTO CWISE INCF INDEX, W GOTO NEW_IDX CWISE DECF INDEX, W NEW_IDX ANDLW .7 MOVWF INDEX ; here W contains the index (either incremented or decremented, depending ; on the direction switch) into the array for the new stepper actuations CALL STEP ; convert the index into a bit pattern MOVWF GPIO CALL DELAY GOTO NEXT ; routine to get step index STEP ADDWF PCL, F RETLW B'00000001' RETLW B'00000101' RETLW B'00000100' RETLW B'00000110' RETLW B'00000010' RETLW B'00010010' RETLW B'00010000' RETLW B'00010001' ; routine to delay between steps DELAY MOVLW .10 ; 10 mSec per step MOVWF DELAY1 DEL_0 MOVLW .250 ; 1 millisecond delay MOVWF DELAY2 DEL_1 NOP DECFSZ DELAY2, F GOTO DEL_1 DECFSZ DELAY1, F GOTO DEL_0 RETURN END

> from the list), hooked everything up and the stepper displays strange > behavior. Sometimes it will turn 1/2 rev then stop and quiver. I accidentally > found that if it would only turn if the wire leads coming out of the motor > were coiled 180 deg around the motor. When I would hold the shaft and > depress the button the motor would turn, unwind the leads then stop a quiver. > If I put the leads straight it the motor will just quiver. I checked the > connections and 3 other motors that all exhibited this behavior. > > I am using a ULN 2803 to drive the stepper. ANy ideas? > > The code I used is designed to half step ther stepper. > http://www.beowulf.demon.co.uk. > The stepper I am using is unipolar, two phase, 6 lead, 12v, 15 deg per step > > > My question is, are all motors capable of half stepping? > What else could be causing this behavior? > Can I change the lookup table to get full steps? > > The fact that the behaviour alters with wire orientation strongly suggests hardware problems. Is the FreeWheel pin on the ULN2803 connected to the motor VCC? Is there sufficient power supply decoupling?.. try a BIG cap (10,000uF per AMP) across the motor supply and / or PIC supply. Coiling the leads around the motor sounds like adding inductance.. a low pass filter is being created in the wires.Reinforcing my suggestions of ULN 2803 freewheel pin and big caps. _____________________________ Lance Allen Technical Officer Uni of Auckland Psych Dept New Zealand _____________________________

part 0 6494 bytes content-type:text/plain; charset="us-ascii" (decoded 7bit) I downloaded the following code to a 16c509 jw chip, which controls a stepper based on a couple of buttons, figured out the wires on my stepper (with help from the list), hooked everything up and the stepper displays strange behavior. Sometimes it will turn 1/2 rev then stop and quiver. I accidentally found that if it would only turn if the wire leads coming out of the motor were coiled 180 deg around the motor. When I would hold the shaft and depress the button the motor would turn, unwind the leads then stop a quiver. If I put the leads straight it the motor will just quiver. I checked the connections and 3 other motors that all exhibited this behavior. I am using a ULN 2803 to drive the stepper. ANy ideas? The code I used is designed to half step ther stepper. http://www.beowulf.demon.co.uk. The stepper I am using is unipolar, two phase, 6 lead, 12v, 15 deg per step My question is, are all motors capable of half stepping? What else could be causing this behavior? Can I change the lookup table to get full steps? ; control a small stepper motor with a 12c509 ; There are two controls, run/stop and direction. ; The motor steps when the RUN button is depressed. ; If the DIRECTION button is pressed the direction ; of rotation is reversed. ; ; Peter Lynch, 13 May 1998 ; .....picKILLspam@spam@beowulf.demon.co.uk ; (this code is NOT certified Year 2000 compliant) LIST P=12c509 include "\mplab\P12c509.inc" OPMASK EQU B'11000000' BMASK EQU B'00101000' ; all bits output (except GP3 and 5) ; GP3 controls run/stop ; GP5 controls direction RUN_BTN EQU 3 DIR_BTN EQU 5 DELAY1 EQU 0C DELAY2 EQU 0D INDEX EQU 0E ; step index ORG 0 ; start of main code MOVWF OSCCAL MOVLW OPMASK OPTION MOVLW BMASK TRIS GPIO ; now go into a loop, output the next bit pattern on ; GP0 - GP4 (GP3 is input only) CLRF INDEX NEXT ; check for the run/stop button BTFSS GPIO, RUN_BTN GOTO NEXT BTFSS GPIO,DIR_BTN GOTO CWISE INCF INDEX, W GOTO NEW_IDX CWISE DECF INDEX, W NEW_IDX ANDLW .7 MOVWF INDEX ; here W contains the index (either incremented or decremented, depending ; on the direction switch) into the array for the new stepper actuations CALL STEP ; convert the index into a bit pattern MOVWF GPIO CALL DELAY GOTO NEXT ; routine to get step index STEP ADDWF PCL, F RETLW B'00000001' RETLW B'00000101' RETLW B'00000100' RETLW B'00000110' RETLW B'00000010' RETLW B'00010010' RETLW B'00010000' RETLW B'00010001' ; routine to delay between steps DELAY MOVLW .10 ; 10 mSec per step MOVWF DELAY1 DEL_0 MOVLW .250 ; 1 millisecond delay MOVWF DELAY2 DEL_1 NOP DECFSZ DELAY2, F GOTO DEL_1 DECFSZ DELAY1, F GOTO DEL_0 RETURN END >> Return-path: Phxsys3KILLspamaol.com From: .....Phxsys3KILLspam.....aol.com Full-name: Phxsys3 Message-ID: <EraseME8de0765d.2517d3fespam_OUTTakeThisOuTaol.com> Date: Mon, 20 Sep 1999 14:16:30 EDT Subject: Stepper code sample for half step- Strange stepper behavior To: PICLISTspam_OUTmitvma.mit.edu, @spam@PHXSYSKILLspamaol.com MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit X-Mailer: AOL 4.0 for Windows 95 sub 26 Hi everyone I downloaded the following code to a 16c509 jw chip, which controls a stepper based on a couple of buttons, figured out the wires on my stepper (with help from the list), hooked everything up and the stepper displays strange behavior. Sometimes it will turn 1/2 rev then stop and quiver. I accidentally found that if it would only turn if the wire leads coming out of the motor were coiled 180 deg around the motor. When I would hold the shaft and depress the button the motor would turn, unwind the leads then stop a quiver. If I put the leads straight it the motor will just quiver. I checked the connections and 3 other motors that all exhibited this behavior. I am using a ULN 2803 to drive the stepper. ANy ideas? The code I used is designed to half step ther stepper. http://www.beowulf.demon.co.uk. The stepper I am using is unipolar, two phase, 6 lead, 12v, 15 deg per step My question is, are all motors capable of half stepping? What else could be causing this behavior? Can I change the lookup table to get full steps? ; control a small stepper motor with a 12c509 ; There are two controls, run/stop and direction. ; The motor steps when the RUN button is depressed. ; If the DIRECTION button is pressed the direction ; of rotation is reversed. ; ; Peter Lynch, 13 May 1998 ; KILLspampicKILLspambeowulf.demon.co.uk ; (this code is NOT certified Year 2000 compliant) LIST P=12c509 include "\mplab\P12c509.inc" OPMASK EQU B'11000000' BMASK EQU B'00101000' ; all bits output (except GP3 and 5) ; GP3 controls run/stop ; GP5 controls direction RUN_BTN EQU 3 DIR_BTN EQU 5 DELAY1 EQU 0C DELAY2 EQU 0D INDEX EQU 0E ; step index ORG 0 ; start of main code MOVWF OSCCAL MOVLW OPMASK OPTION MOVLW BMASK TRIS GPIO ; now go into a loop, output the next bit pattern on ; GP0 - GP4 (GP3 is input only) CLRF INDEX NEXT ; check for the run/stop button BTFSS GPIO, RUN_BTN GOTO NEXT BTFSS GPIO,DIR_BTN GOTO CWISE INCF INDEX, W GOTO NEW_IDX CWISE DECF INDEX, W NEW_IDX ANDLW .7 MOVWF INDEX ; here W contains the index (either incremented or decremented, depending ; on the direction switch) into the array for the new stepper actuations CALL STEP ; convert the index into a bit pattern MOVWF GPIO CALL DELAY GOTO NEXT ; routine to get step index STEP ADDWF PCL, F RETLW B'00000001' RETLW B'00000101' RETLW B'00000100' RETLW B'00000110' RETLW B'00000010' RETLW B'00010010' RETLW B'00010000' RETLW B'00010001' ; routine to delay between steps DELAY MOVLW .10 ; 10 mSec per step MOVWF DELAY1 DEL_0 MOVLW .250 ; 1 millisecond delay MOVWF DELAY2 DEL_1 NOP DECFSZ DELAY2, F GOTO DEL_1 DECFSZ DELAY1, F GOTO DEL_0 RETURN END